1. Field of the Invention
The present invention relates to a method for insulating with insulating tubes, leads of a non-reversible thermal fuse that is used in small transformers, heat sinks, or power transistors for domestic and industrial apparatus as a safety measure, and is fused at a temperature above an allowable temperature.
2. Description of Related Art
FIG. 1 shows a conventional axial-type thermal fuse. The circumference of leads 3 of this type of thermal fuse may be insulated with an insulating tubes 4 as a safety measure.
FIG. 2 shows a conventional radial-type thermal fuse. The circumference of leads 3 of this type of thermal fuse may also be insulated with insulating tubes 4.
In FIGS. 1 and 2, the leads 3 may be insulated with insulating tubes 4 during the manufacturing process of the thermal fuse, or insulated with insulating tubes 4 after the thermal fuse made with non-insulated leads 3 has been manufactured.
In the latter case, the insulating tubes 4 are put on the circumference of the leads 3, and when an end of the insulating tube 4 contacts a seal 2 of the thermal fuse, it is fixed to the seal 2 by applying an adhesive 5 around the end of the insulating tube 4.
In this case, since the adhesive 5 is heaped around the end of the insulating tube 4 and the seal 2 as a band, the quantity of the adhesive 5 may increase, the adhesive 5 may overflow to a side of the case to degrade the appearance, and the value of the product may be lowered.
A thermal fuse is provided with a fusible alloy that constitutes a fuse element, and a resin-pellet-type fusible alloy is generally used. However, such a fusible alloy has problems of a high unit price, and a large size.
The leads 3 are plated with 100% tin (Sn), which has a problem of low heat resistance when being soldered.
An object of the present invention is to provide a method for insulating leads of a thermal fuse with insulating tubes, for reducing the quantity of an adhesive used, and preventing the adhesive from heaping at the seal, by applying the adhesive around the circumference of the leads, putting insulating tubes on the leads from the outer ends, rotating the insulating tubes so that the adhesive is present inside the insulating tubes. It is another object of the present invention to provide a thermal fuse intended to reduce the costs of the thermal fuse by using an alloy having a melting point of 190xc2x0 C. or above as the fusible alloy 6, and intended to improve the heat resistance of the leads by plating the leads with an alloy of tin (Sn) and copper (Cu).